Continued frustration filling body tube grooves

Wow, so many responses. I'll try to sum up my responses.

When sanding, I move in little circles. I don't wrap the paper around the rocket - that was a mistake I made on my first. - well, second (the first where I was aware of any filling techniques). For sanding the primer, I didn't use my sanding block, my reasoning being that I was sanding a round surface. I also wanted to feel what I was doing, as much as possible. I used a small bit of paper and the pads - not the tips - of my fingers.

I think I'm definitely bearing down too much. But even if I'm not doing what I do here, even if I don't wet sand the primer, I've had this problem before. I've filled the tube first, before gluing anything on or priming or any of that, and when I try to remove the excess, I end up scuffing the tube. Perhaps this just needs a lighter touch.

I really don't know where the scratches came from, because I wasn't moving back and forth. I don't think. I feel pretty sure I kept moving in little circles. Perhaps I got lazy or distracted on certain parts of the tube and moved it back and forth.

I thank you all for the advice here. Some of you, I've seen your rocket pictures, and I really respect your expertise.

When I was here earlier, I read all the replies that had been posted up to that point, and thought "oh, of course! I shouldn't have wet sanded the primer!"

And then I sat down to relax and watch the free DVD that came with my first Apogee Components purchase (guillotine fin jig - I'm so excited!). Tim Van Milligan went through the basics of rocket building, painting, etc... And DARN IT, if he didn't wet sand his primer! I literally shouted at the screen, "but I just learned I'm not supposed to do that!" But then his rocket turned out really smooth and shiny - even the primer was shiny, and I thought how in the heck do you make primer shiny?? He lightly dry sanded first with a coarser paper, then wet sanded with 320 (I think) and then 600. But he started with a nice, thick multi-coat of primer. Whereas I had already sanded most of mine off and could see some of the BT underneath.

So I'm still confused, because I've seen so many different approaches, and I'm not sure what will work best for me. But I'm taking all your advice into... advisement? (That sounds redundant). I think I just need practice. I have a body tube that was partially squashed by the USPS, and I think I'm going to cut off the squashed part and practice with it (I could use it, but I'm not ready to build my own designs as yet).

In any case, whether it's a bad idea or a fine idea, based on the pictures some of you have posted, I'm sure the wet sanding is clearly not necessary to get a good finish. DizWolf's rocket looks really nice, Luke Strawwalker has given me some really good advice on several of my threads (I particularly liked the fin papering pictures you linked me to), and JohnCoker's website helped me when I first started painting my rockets. You guys all seem like really competent rocketeers, and I thank you for your help.

You're welcome...

You've got the right idea... practice, practice, practice...

Michaelangelo didn't make his "David" statue on his first try... those guys that make those miles-deep super glassy wet-look paint jobs at the car shows started off just like you or I... from scratch, with their first paint job... like playing an instrument, or a sport, or any other skill, it all comes down to proper techniques and materials and practice, practice, practice...

Later and best of luck! OL JR

JohnCoker said:

I take a first pass at filling the grooves before priming, then do the prime/sand/fill cycle until I'm satisfied. It does sound like you're sanding too much, but 400 grit doesn't seem excessively coarse to me.
Edit: I missed it the first time, but I agree that wet-sanding paper tubes is likely to cause trouble. Wet sanding is great, but only on waterproof materials.

Click to expand...

Ditto!
John knows his stuff! LPR and HPR.

Here's some food for thought, In time you'll find your own methods:
https://modelrocketbuilding.blogspot.com/2010/09/carpenters-wood-filler-mix-ratios.html
https://modelrocketbuilding.blogspot.com/2013/02/wet-sanding-thoughts.html
https://modelrocketbuilding.blogspot.com/2010/10/make-that-sandpaper-last.html

Again, this is just how I do it.

Wet sanding the first coats of primer are too close to the tube surface.
Wait until the tubes, fins and nose cone are sealed (dried color coats) before wet sanding.
I use a LOT of 400 grit. It loads up quickly with primer.
Hang in there, you'll learn something new in every build. Your blog is a great way to record your results.

Best way to fill the spirals is to not ta.


TA

hcmbanjo said:

Ditto!
John knows his stuff! LPR and HPR.

Here's some food for thought, In time you'll find your own methods:
https://modelrocketbuilding.blogspot.com/2010/09/carpenters-wood-filler-mix-ratios.html
https://modelrocketbuilding.blogspot.com/2013/02/wet-sanding-thoughts.html
https://modelrocketbuilding.blogspot.com/2010/10/make-that-sandpaper-last.html

Again, this is just how I do it.

Wet sanding the first coats of primer are too close to the tube surface.
Wait until the tubes, fins and nose cone are sealed (dried color coats) before wet sanding.
I use a LOT of 400 grit. It loads up quickly with primer.
Hang in there, you'll learn something new in every build. Your blog is a great way to record your results.

Click to expand...

OK, I think I'm gonna go with the majority consensus on this one, especially with you, John and Luke Strawwalker all saying the same thing. Tim Van Milligan's rocket looked great in the video, but I think there's too much chance that I'd screw it up if I wet sanded primer. Thanks for the links - I've looked at your blog a lot, but I hadn't seen the sanding pages.

I still need to get better at not scuffing the tube when sanding off the filler. That's been a real problem for my surface prep.

I carefully wet / damp sand the final finish primer coat.

The one time I damp sanded a paper tube I rashed it up all to hell in literally 3 seconds..fixed with zap and never ever ever wet sanded a tube spiral or 1st coats of primer. ...only the final finish coats now.

Kenny

If you really want practice sanding rockets, I'll send you one to sand!

I've got one in primer just sitting there ready to be sanded, and here you are with nothing to sand! It's perfect!

PM your address, and I will send it to you, along with a can of color coat. You send it back to me finished!

lcorinth said:

When I was here earlier, I read all the replies that had been posted up to that point, and thought "oh, of course! I shouldn't have wet sanded the primer!"

And then I sat down to relax and watch the free DVD that came with my first Apogee Components purchase (guillotine fin jig - I'm so excited!). Tim Van Milligan went through the basics of rocket building, painting, etc... And DARN IT, if he didn't wet sand his primer! I literally shouted at the screen, "but I just learned I'm not supposed to do that!"

Click to expand...

LOL! Oh, man! That was funny!

No one has mentioned the easy way. Just use a hi-build primer. https://www.duplicolor.com/products/fillerPrimer/ Spray along the spirals and then cover the whole airframe. Let dry and sand. Repeat once and you're done.

Bob

My latest technique seems to work... I can't say that I'm the origin of the method though. Using a low tack masking tape, wrap two bands of tape around the body tube with the spiral between them. Using a high build primer (Rusto's Filler Primer in my case) spray a heavy coat into the spirals, then remove the tape once I'm satisfied that they are filled (while the paint is still wet). After the primer is dry, I spray the whole rocket with primer and allow the rocket to dry completely. On the primer coat I use 320 grit wet dry sandpaper, but I don't use any water in the process of sanding it.

I haven't wet sanded rockets until recently, but I don't use much water, just enough to keep the paint from forming little balls that keeps the sandpaper from working. It's not fiberglass, where you go at with a big bucket (it's also pretty easy compared to a 26' boat!!). If I cut through the paint somewhere, I stop immediately and wipe it off, means went too far but sometimes have to do that to find out.

Very interesting thread. I'm going to try watered-down joint compound on my next build.

I agree with the hi build primers. I have only painted a couple rockets but paint on cars everyday. On my rockets I primed first with a urethane primer then sanded and filled any imperfections with a spot putty then primed again dry sanded with 320 and painted. It didn't seem like a good idea to wet sand since the rocket was card board but if u use spray can primers they are not activated and take a while to dry so a little wet sanding will help with the sand paper loading up. As far as the fuzzys just re prime and sand until they are gone

I too hate Spirals. I've gone so far as to Paper the Tubes to cover them on some Builds.

K'Tesh said:

My latest technique seems to work... I can't say that I'm the origin of the method though. Using a low tack masking tape, wrap two bands of tape around the body tube with the spiral between them. Using a high build primer (Rusto's Filler Primer in my case) spray a heavy coat into the spirals, then remove the tape once I'm satisfied that they are filled (while the paint is still wet). After the primer is dry, I spray the whole rocket with primer and allow the rocket to dry completely. On the primer coat I use 320 grit wet dry sandpaper, but I don't use any water in the process of sanding it.

Click to expand...

The first place I saw that seam fill method was on the George Gassaway website.
He used it on the large diameter tubing on his Little Joe II.

https://georgesrockets.com/GRP/CONTEST/TIPS/N-50/scale.htm
Scroll down about halfway, under "Finishing".

I DO damp sand primer (I call it that because the technique is markedly different enough to 'wet sanding' as it's done on classic auto finishes that I don't feel like it should be called by the same name) and I've done it with great success... it's how I do MOST ALL my builds as a matter of fact.

BUT, I make sure I have PLENTY of primer on first (at least 3-4 good heavy coats) and have done the majority of the sanding with 220 grit dry followed by 400 grit dry. Basically the surface would be considered "good enough" for paint by most rocketeers before I ever bother with damp sanding. I use Rustoleum WET SANDABLE primer (says so RIGHT ON THE CAN) and basically just lightly damp sand the surface enough to eliminate any remaining sanding scratches and minor imperfections in the surface. Basically, I've already done 95% of the "removal of material" sanding with the previous 220 grit and 400 grit dry sanding passes, and reapplied primer to any areas that those applications haven't cleaned up or smoothed out, or where the primer sanded down to the tube or balsa. Basically, the ENTIRE SURFACE should have a good coat of primer left before damp sanding-- there should be NO exposed tube or balsa surfaces, and none likely to be uncovered by damp sanding. Sand-throughs in damp sanding can turn messy and require quite a bit of additional work to correct as seen in the OP's pics... it is NOT a "beginner's technique"... IOW, someone should be very proficient at getting good results with dry sanding techniques and such BEFORE attempting damp sanding of anything. It's basically a "take it to the next level" technique.

Damp sanding "wet sandable" primer WILL make it shine. In fact, this is how you detect any flaws in the surface... by observing the "glint" of reflected light from a distant lamp or chandelier or brightly lit window on the other side of the house reflected off the surface of the rocket when held up toward this light source and slowly turning and/or tilting the rocket to observe the reflected light... any imperfections in the surface will show up as dark spots, mottles, waves, or broken reflections in the reflected light versus a nice, clean, smooth reflection of the light. (Basically it's the same was a DVD or CD works-- reflecting laser light off a surface modified with imperfections into which the data has been codified, and observing those reflections for the imperfections and inferring the data stored by the patterns of imperfections in the reflected light.) These can then be fixed according to the severity of them, or the desires of the person building the rocket.

I like to see a "dull shine" in the primer, but not take it to a really glossy surface-- that would eliminate most of the "tooth" (make the surface SO smooth that paint would have a really hard time adhering to the surface). A light shine or dull shine is enough to make sure the imperfections and sanding scratches are gone and the surface is nice and smooth and ready for paint. Some folks say paint will 'cover the scratches' but that's certainly NOT been my experience... paint tends to MAGNIFY any existing defects in the surface preparation work, NOT COVER THEM UP. If you lay on the paint long enough and thick enough you can probably cover most MINOR sanding scratches, and still obtain an acceptable finish, but personally I don't like putting on that much paint... I'd rather put on more primer, and sand most of that off, to obtain a clean, smooth, great looking finish than continue to slather paint on the surface hoping it will cover and blend the poor or incomplete prep work. That's just me, though, and "to each his own"...

Basically, if in doubt, watch some videos on "DIY car body/paint repairs" and such... most of the techniques (with the exception of wet sanding using a dribbling garden hose on the surface of the paint) are pretty much EXACTLY the same. Substitute "carpenters wood filler" (CWF) for "body filler" (Bondo, etc.) and you'll get the idea... the steps and techniques are very much alike, practically the same. You'll even see Bondo Glazing and Spot Putty used to "float out" any final imperfections in the surface, much as I do with tube spirals and such. Then its all sanded out to a final smooth finish, usually with a sanding bar (which is great for cars but not as much use for rockets-- small sanding blocks and sponges and stuff are best for our size work, or fingers IF you have good techniques and don't exert too much pressure, especially too much pressure on one spot or area... the pressure HAS to be even to get good sanding results REGARDLESS OF METHOD, and basically, the less pressure THE BETTER!) Autobody techniques then typically apply a few coats of primer, sand those down uniformly and smoothly (dry, as most auto primers are porous and not designed for exposure to weather and moisture and of course wet sanding) then applying multiple color coats. Depending on the "paint system" (as there are MANY different types of paints and chemistries, and different methods are required to apply them based on their individual types and recommendations-- follow the manufacturer directions for their paint system) there are several different ways to go from this point. Clearcoats are usually applied over paints designed for them at this point, usually several coats, and then depending on the "depth" of the finish desired, this can be followed by myriad different wet sanding steps in progressively finer grits, culminating in several steps of progressively finer buffing agents, and finally polishing compounds to make the surface glass-smooth to get that "mile deep wet look". Some paints don't use clearcoats and, if desired, go through much the same treatment with multiple grits of buffing compounds, polishing compounds, and final waxing and polishing. Most of it depends on the final desired finish-- the more work, the more expensive and difficult it is to maintain (and the more easily it's damaged, generally speaking!) Personally I've found that if I do the surface prep right, there's NO NEED for wet sanding color coats... screwing up and sanding too deep on a color coat means basically you have to do the color coats from scratch, and I don't like going back that far. If something's going to get screwed up, I'd rather it be a primer coat that is EASILY and quickly fixed... (but that's just me). I find that if the surface prep looks terrific BEFORE the color coats go on, IF one puts the color coats on PROPERLY (without drips, sags, runs, orange peel, dry spray, humidity blushing, etc) then the final color coat appearance will look great and there's absolutely NO REASON to wet sand or damp sand the color coats... it'll be ready for clear coat (if desired) or call it "done" at that point.

It's really a matter of developing techniques that work FOR YOU, according to your own style and skills and abilities, and then deciding just what your goals are and how far you want to take it.

Best of luck! OL JR

Not EVERYTHING needs a "glass smooth mile-deep wet look" finish. If that's your thing go for it, but lets face it... while it might look great on a particular rocket, there's not much reason taking it to that level on an Alpha III...

+1 to Bondo spot and glazing putty. I have also used thinned joint compound but Bondo is my favorite. In some cases, I have thinned it with lacquer thinner and brushed it on in layers. I use the stuff for rockets, scale modeling and field expedient temp repairs on non structural areas for real life helicopters (thin BSGP until it will pour slowly and apply with glass cloth for more possibilities).

I Strongly discourage the use of damp or wet sanding on any primer as it is completely unnesseary and can no Will lead to the kinds of probelms the OP has experienced.

I'll say this again one more time! Many Primer Cans do say to wet sand but we must remember these primer are manfactured and sold with the intent to be used On Automotive exteriors or used on Metal Substates NOT water absorbing wood, Cardboard or phenolic.
Unnecessay YES! Totally Unnecessary because one gains absolutely NO useful advantage DRY sanding ANY primer beyond 360 grit. The gloss factor of your paint will remain unchanged be it rattle can or applied with a spray gun but gains adhesion using the micro scratches left by 360 sandpaper. Wet sanding or "Damp" sanding primer...ANY Primer makes even less sense when the primer is applied to a carboard or phenoic substrate with can be badly damage by absorbing moisture.

I'll say this one more time. Save yourself a ton of time and unnecessary labor....DO NOT damp or wet sand PRIMER on model rockets.

Wet and or Damp Sanding should be limited to the final Color coat of your finish to remove dust or lint or other very fine surface imperfections in that final coat.

Nobody has mentioned the easiest method I have found for dealing with spirals. Skip the paint job. I have yet to hear a comment on my spirals for a rocket with no finish job. Another easy method is to let my daughter use markers for the finish.

But on a more serious note, I have found I like to use one very light coat of primer. Then use a contrasting high fill primer color. If I start to see the other color come through I stop immediately and add another layer of high fill. This does add weight, but I normally don't care.


Kirk

bobkrech said:

No one has mentioned the easy way. Just use a hi-build primer. https://www.duplicolor.com/products/fillerPrimer/ Spray along the spirals and then cover the whole airframe. Let dry and sand. Repeat once and you're done.

Bob

Click to expand...

I hadn't heard of that! This might be the solution for me, because with the CWF route, I always seem to raise little shreds on the tube, regardless of wet sanding or dry sanding. Just trying to get the darn CWF down to surface, I scuff the surrounding area of the tube.

I'm going to look for this stuff.

luke strawwalker said:

I DO damp sand primer (I call it that because the technique is markedly different enough to 'wet sanding' as it's done on classic auto finishes that I don't feel like it should be called by the same name) and I've done it with great success... it's how I do MOST ALL my builds as a matter of fact.

BUT, I make sure I have PLENTY of primer on first (at least 3-4 good heavy coats) and have done the majority of the sanding with 220 grit dry followed by 400 grit dry...

Click to expand...

OK, that was a lot of great information and it makes the Apogee Components video make much more sense to me. You see, in the video Tim Van Milligan laid down a really heavy coat of primer - he even said, "This is way more than you want for painting. I've even got some drips here, but I'm going to sand that all off." So he had a lot of primer to sand through.

I bought a cheap, 7 dollar rocket I might try this on next (I buy cheap little ones and consider them "practice rockets" for the more expensive ones - if I mess up the finish, I'm disappointed, but only 7 bucks' worth). If it doesn't work, I'll skip the damp sanding from now on. But it sounds like it might be worth a try on a cheapie.

I still have the problem of scuffing the tubes any time I try to fill spirals, but I might try the filler primer method for that particular problem if I don't get better at sanding off only the CWF. Thanks for clearing that up!